In recent years, a device utilizing light emission from an electroluminescent element (light emitting element) has attracted attention as a device for display, lighting, or the like. As the light emitting element used in such a device, well-known is a light emitting element in which a layer containing a light emitting compound is interposed between a pair of electrodes.
In such a light emitting element, a hole injected from one of the electrodes is recombined with an electron injected from the other to form an excited molecule. When the excited molecule returns to a ground state, light is emitted.
Meanwhile, there is a strong demand particularly for lower power consumption of a display device to be incorporated in various information processing devices which has been rapidly developed in recent years. In order to achieve this, it has been attempted to lower the drive voltage of the light emitting element. In view of commercialization, it is also important not only to lower the drive voltage but also to extend the life of the light emitting element. Thus, a light emitting element to achieve this is under development.
For example, Reference 1 aims to realize lower drive voltage and longer life of the light emitting element by using, as an anode, metal oxide with a high work function, such as molybdenum oxide (Reference 1: Japanese Patent Laid-Open No. 9-63771).
However, the method disclosed in Reference 1 cannot provide the element with sufficient reliability, and has not reached a practical level. Therefore, technology development to realize reliability or further longer life of the element has been needed.